RF through water question

What are the design issues involved with passing medium wave ( 10s of MHz ) higher power ( KWatts) RF through a water jacket. Assume "tap" water and of course non conductive non ferrous housing material.

Ron H.

Reply to
Ron H.
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Reply to
Scott Stephens

Um.. unless your water is de-ionized or distilled, you don't pass RF through it. It gets absorbed and turned into heat just like in a microwave oven. Tap water is not de-ionized.

Reply to
crusty

At a frequency somewhere around 1 gigahertz, water (even pure water) changes from a dielectric to a lossy dielectric. At frequencies well below 1 gigahertz, water should perform much like any other high dielectric constant material, with loss depending mainly on the conductivity and thus the ionic contaminants.

See:

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Reply to
John Popelish

How do you think they talk to submarines? (the answer is: slowly!) You can pass RF through water (even sea water), but unless it's very low frequency (or extremely low - ELF) it doesn't get very far. You'd get serious attenuation with 10s of MHz.

Tim

Reply to
Tim Auton

For the most part, with acoustic signaling. And sub-20kHz ELF, but only if the sub is near the surface and trailing an antenna.

Thanks, - Win

(email: use hill_at_rowland-dot-org for now)

Reply to
Winfield Hill

in article c7qt90$mej$ snipped-for-privacy@tuvok3.mmm.com, Ron H. at snipped-for-privacy@mmm.com wrote on 5/11/04 8:59 AM:

Read and understand one of my favorite texts or one of its successors: Ramo and Whinnery, "Fields and Waves in Modern Radio." Learn how to calculate skin depth. Look up appropriate values for conductivity and dielectric constant. End up by doing the calculations. They are easy using a modern scientific calculator.

Otherwise, send me a check for $200, and we can negotiate what you get for that.

Bill

Reply to
Repeating Rifle

AFAIK VLF (3-20kHz) is only used near the surface with a trailing antenna, but the latest ELF systems have neither requirement. What I can find on the ELF system in use by the US (76Hz) suggests they can receive ELF at operational speed and depth, which doesn't suggest "near the surface" to me. It's all relative of course and hard figures are hard to come by (hardly surprising!), but I've seen 2-300m mentioned. AIUI they use on/in-hull antennas (presumably SQUID based) instead of trailing wire antennas for ELF too.

OK, perhaps it's not how they /usually/ talk to submarines though :)

Tim

Reply to
Tim Auton

"Repeating Rifle" in news:BCC6A5B1.173B6% snipped-for-privacy@sbcglobal.net...:

Or if you are really, really desperate, search Usenet archives for the phrase "skin depth" in the year 1987.

There you may read (with growing awe, if you know the subject) one Commander Brett Maraldo describing speaker cables of mercury-filled tubing, and an ensuing Grand Debate -- as popular then as now -- on skin depth in conductors: one camp insisting that depth of penetration is the electrical wavelength at frequency, and the other group countering that it's the (!) acoustical wavelength instead.

(At that time, and also in a follow-up, I too cited Ramo and Whinnery. For what good it did, but maybe it did, who can say?)

Max

Reply to
Max Hauser

"The other John Smith" in message news:fRhoc.17005$ snipped-for-privacy@newsread1.news.pas.earthlink.net...

You're damn right it does. (The intuitive notion of a tight relationship between bit rate and analog bandwidth disappears like parted waters if you study communication theory -- you can have data rates far greater or far less than bandwidths, in exchange for requirements for SNR or other constraints.) But the subject tends to the counterintuitive, so it collects notions and suppositions and opinions. (Like various other areas of electronics.) This by the way is partly the domain of the newsgroup comp.dsp .

Reply to
Max Hauser

in article snipped-for-privacy@corp.supernews.com, Max Hauser at snipped-for-privacy@THIStdl.com wrote on 5/11/04 11:20 PM:

I sometimes wonder about the sanity of some audiophiles. Although many do indeed know what they are talking about, others are like Art Bell. What else would explain the love affair with tube ampifiers, monster litz cables, vinyl records over compact disks, and my favorite, a green marker to green up the area around a CD spindle hole? To tell the truth, I have not heard much about that last on letely. Is it still in vogue?

Bill

Reply to
Repeating Rifle

In message , Winfield Hill writes

[snipped]

I bet they're mightily pissed off by HTML messages.

Cheers

Reply to
Keith Wootten

Yes, and no binary attachements allowed.

Thanks, - Win

(email: use hill_at_rowland-dot-org for now)

Reply to
Winfield Hill

bet they get rid of popup ads as well

martin

Three things are certain: Death, taxes and lost data. Guess which has occurred.

Reply to
martin griffith

In article , Winfield Hill wrote: [....]

This is why a familigram might say something like this "..Born 010613 1+ ok". Until the sailor comes home he doesn't know the eye color of his kid.

BTW: They don't trail anything to receive, as far as I know. Trailing something isn't something they want to have to do to get orders. They do trail a sonar array which looks like a firehose on the end of a longish cable. The sonar array isn't deployed all of the time and they can chop it off if they have to.

Reply to
Ken Smith

On a sunny day (Wed, 12 May 2004 13:03:19 +0100) it happened Keith Wootten wrote in :

LOL

Reply to
Jan Panteltje

Boy, I would love to correct some of the mis-information expounded in this thread so far. It's been over thirty years since my last cruise in a fleet balistic missile submarine and I'm not sure how much of what I know is still classified. I will tell you that family grams were limited to about 20 words each and 3 per patrol. The boat was nearly continuously receiving civilian teletype news feeds (AP,UPI, REUTERS). Reception of relatively high speed message traffic was never a problem at our normal operating depth. Transmitting, however, is/was somewhat problematical. FBMs due to their mission DO NOT transmit/radiate any more energy than they have to. Most equipment with the ability to generate a signal had its fuses pull to preclude accidentally exposing the boats position. That included radio, radar, and sonar.

ARM

Reply to
Alan McClure

A teacher at my college told me that somewhere (i cant have been listening) they use the granite rock as an antenna, and then drill down however amny miles apart and make a connection.

not sure if he was talking aout of his...

Tim

Reply to
Tim Fish

Actually it could not be much of a secret when people were lighting thier homes with the signal off the antenna.

Reply to
bushbadee

We did have a 'floating wire antenna', but it was not for ELF. It's use was discouraged because 1) you had to be going slow and near the surface in order for it to float to the surface, 2) quite often seagulls or other birds would sit on it. The sight of 4 or 6 seagulls making 3 knots through the ocean in a line was something to see through a periscope, but obviously it gave away our position to anyone nearby.

daestrom (former submariner)

Reply to
daestrom

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